Hacking Firefox – about:config
Many of Firefox’s settings aren’t exposed through the Tools > Options menu; the only way to change them is to edit them manually by typing about:config in the adress bar.
You will get a list of all firefox settings and extensions. I found a couple of interesting ones, but remember to keep a log of everything you change, or make backups.
Select just a word
The Boolean preference layout.word_select.eat_space_to_next_word governs one of Firefox’s tiny, but for me incredibly annoying, little behaviors. When you double-click on a word in a Web page to select it, Firefox automatically includes the space after the word. Most of the time I don’t want that; I just want the selection to stop at the end of the word. Setting this to false will defeat that behavior.
Swap out to disk memory when minimized (Windows only)
A little-known feature in Firefox allows the Windows memory manager to swap out some of Firefox’s physical memory space to disk when Firefox is minimized but not closed. This allows other programs to use the physical memory that Firefox was previously monopolizing.
By default, this feature is turned off, for two reasons:
1) PC memory is generally more plentiful than it used to be, so it makes sense to use it if it’s available
2) swapping Firefox’s memory out to disk will slow the program down when it’s restored.
That said, if you run Firefox side by side with other memory-hungry applications, it might help keep them from competing with each other. To enable this feature, create a new Boolean preference called config.trim_on_minimize and set its value to true.